This invention relates to an X-Y plotter, and more particularly, to an X-Y plotter of the type wherein a non-perforated recording paper is fed to the X-Y plotter for recording.
An X-Y plotter of this type, which requires no guide perforation in a recording paper, is disclosed, for example, U.S. Pat. No. 4,683,480, wherein since no guide perforation is required for the recording paper, and low-weight paper can be used, a high speed plotter can be obtained without using any complicated paper feed mechanism, resulting in a reduced sized X-Y plotter.
For developing an X-Y plotter of the above-mentioned type, one of the most important problems to be solved lies in its paper feed mechanism. There is required a special paper feed mechanism which can move or feed the paper in an exact manner without slippage with respect to the non-perforated paper.
The X-Y plotter of the above-mentioned U.S. Patent comprises a cylindrical drive or feed roller, the outer surface of which is formed with a plurality of projections fabricated by machining the surface in the circumferential and axial directions, with each of these projections having a top sharpened by machining, which thrusts into the paper, and prevents slippage between the paper and the roller.
The thrust depth of the projection, however, is not maintained constant, but varies in dependence upon the thickness or the hardness of the paper, because there is provided no means or reference plane which ensures to maintain the thrust depth of the projections constant. This unfavorable phenomenon of the prior art is significant in the case of a thin and flexible recording paper, where the thrust depth is gradually increased during a paper feeding operation, and at last adjacent thrust holes may be joined together, causing break down of the recording paper.